1. Field of the Invention
The present invention relates to a methane analyzer using a so-called cutter method in which a cutter chamber removes those hydrocarbons other than methane (hereinafter referred to as "nonmethane hydrocarbons") contained in a sample gas as a preliminary process step of a hydrogen flame ionization detector system (hereinafter referred to as "FID") and, more particularly, to a controlled dilution of the sample gas prior to submission to the hydrogen flame ionization detector.
2. Description of Related Art
In a methane analyzer, as disclosed, for example, in Japanese Utility Model Publication No. Sho 62-8524, a cutter chamber can be provided in a prestage or first portion of an FID, and an oxygen gas passageway can be provided with a flow rate regulator connected with the cutter chamber to supply oxygen to the cutter, whereby the process step of burning (oxidizing) the nonmethane hydrocarbons, contained in a sample gas, is used to remove them, followed by burning the sample gas, from which said nonmethane hydrocarbons have been removed, in the FID.
It is, however, necessary to keep the concentration of oxygen supplied to the cutter at an appointed or greater value (for example, 15% by volume or more) in order to burn the nonmethane hydrocarbons in the cutter chamber. Accordingly, a CVS dilution measuring method, in which an exhaust gas as a sample gas is diluted with air, has been used in order to analyze an exhaust gas from motorcars by a methane analyzer of this type. Thus, methane has been unable to be measured directly without diluting the exhaust gas.
In addition, in a methane analyzer as disclosed in Japanese Utility Model Publication No. Sho 62-8524, it is also necessary to provide an oxygen cylinder separately from the air supplied as the operating air for the FID. Thus, disadvantages have occurred in that the methane analyzer of this type is further complicated in construction and expensive.
Thus, the prior art is still seeking to provide an improved methane analyzer system.